Scientific Method —

Cool cooling

Microelectro-mechanical pump may provide a new way to cool computer chips.

One of the problems with cooling silicon chips is that the heat must make it to the surface of the chip and through the packaging before it can be spread out on a big plate and dissipated by some sort of heat exchanger. This can lead to the chip itself running at some pretty high temperatures. The problem is only going to get worse with transistor density and computational demands increasing all the time. One approach is to actively control the amount of power dissipated by the chip. In digital circuits this is done by varying the voltage, by actively switching off parts of the chip, and by varying the clock speed. However, these measures would not be so necessary if there was a more efficient way of extracting heat.

Enter a bunch of engineers from the cow university of Purdue . They have taken two existing technologies and managed to make them work together in a very clever way. The first technology is microfluidic channels. These are basically little grooves that sit inside a chip and allow liquid (not milk) to flow through them. They are usually associated with biological sensors and reactors, however the Purdue based group recognized that the fluid flowing through the channels represented a very good mechanism for removing heat from the chip itself. The problem is that the pump would have to sit off the chip, involve moving parts and therefore break. Enter ion pumping. By adding ions to the cooling fluid, the whole liquid can be moved by using an electric field. Thus the pump is incorporated on the chip by placing electrodes along side the microscopic channels. The fluid is pumped by alternately varying the voltage across the electrodes. Unfortunately, at microfluidic scales this is not enough. To get the amount of force required, a piezo electric material was incorporated onto the chip as well, and this material squeezes the channels to provide extra pumping in addition to the ion induced flow.

The cooling is very power efficient, requiring only microwatts to extract milliwatts of heat. However, there is much scaling to be achieved before this will turn up on the latest and greatest from Intel.

Chris Lee
Chris writes for Ars Technica's science section. A physicist by day and science writer by night, he specializes in quantum physics and optics. He lives and works in Eindhoven, the Netherlands. Emailchris.lee@arstechnica.com//Twitter@exMamaku